Phytoremediation of mildly contaminated, wastewater-irrigated soils using mixed planting of Brassica juncea and Urtica dioica.

Soil contamination with toxic heavy metals is a critical concern in areas irrigated with industrial and domestic wastewater. This study assessed the phytoextraction potential of Brassica juncea (Indian mustard) and Urtica dioica (stinging nettle) under mixed planting for the remediation of cadmium (Cd), lead (Pb), and nickel (Ni). Surface soils (0-15 cm) were collected, filled into 8-kg pots, and planted at a density of 50 plants m^-2 (35 B. juncea, 15 U. dioica), followed by 60 days of wastewater irrigation. Metal accumulation exhibited a root > stem > leaf distribution in both species, with B. juncea recording higher concentrations (Cd: 634.36 mg/kg; Pb: 563.54 mg/kg; Ni: 445.68 mg/kg) compared to U. dioica (Cd: 317.18 mg/kg; Pb: 305.92 mg/kg; Ni: 222.84 mg/kg). Soil mass balance revealed reductions of 74.8% for Pb, 38.0% for Cd, and 39.2% for Ni, corresponding to removals of 307.30 mg/m². Phytoremediation indices (bioconcentration factor (BCF), translocation factor (TF), and efficiency) confirmed Pb as the most effectively removed element, with B. juncea extracting ∼68.5% of soil Pb in one cycle. Statistical analysis (mean ± SD; 95% CI) validated these reductions. Mixed planting improved uptake by combining high biomass with efficient extraction, highlighting a cost-effective, sustainable approach for remediating wastewater-irrigated soils.